This invention relates to an electronic blasting capsule.
The specification of international patent application number PCT/ZA2006/000037 describes a drilling machine which uses a drill bit, attached to a drill rod, to drill a hole in a rock face. The drill rod and drill bit are left in situ in the hole and a pressurised source is used to direct a propellant cartridge along passages in the drill rod and drill bit. In one situation the cartridge is ignited by causing the cartridge to impact against a wall of the hole. This can be somewhat unreliable.
It is known in the technology field which relates to missiles, shells and other projectiles, to transfer energy to a fuse on a projectile using a microwave or other suitable electromagnetic energy source. In U.S. Pat. No. 4,495,851 two-way communication is established between a shell and a control location in order to set and monitor the operation of an electronic fuse. U.S. Pat. No. 4,237,789 describes a projectile fuse which has electronic circuitry for receiving radiated signals. The fuse includes a fusible link which alters the operation of control circuitry. The projectile has no on-board intelligence and the link is fused in order to arm the projectile. U.S. Pat. No. 4,144,815 also relates to a fuse, in a projectile, which is set by a remote microwave source. One-way communication is established from a control to the projectile and circuitry associated with the fuse is biased so that it can subsequently receive data.
U.S. Pat. No. 4,160,416 makes use of an electromagnetic induction technique to transmit a signal to timing circuitry on a projectile which, apart from timing circuitry, has no on-board intelligence. U.S. Pat. No. 4,300,452, which also makes use of magnetic induction, describes the geometry of a suitable inductive link.
U.S. Pat. No. 4,632,031 refers to the remote arming of a projectile or missile. Optical communication is established with the projectile in order to program or operate a timing mechanism. U.S. Pat. No. 3,760,732 describes a system which makes use of RF signals, not magnetic coupling, to establish one-way communication with a projectile.
Other documents which are representative of the prior art, in this respect, are EP 1559986, EP 134298, U.S. Pat. No. 6,760,992, WO 2006055953, EP 235478, WO 20060702039, DE 4302009, U.S. Pat. No. 6,543,362 and EP 1126233.
Techniques in the prior art documents referred to are not suitable for use with a blasting capsule which can be initiated in a reliable and safe manner and which is suitable for use in a drilling machine of the aforementioned kind. An object of the invention is to provide a capsule of this type in which the likelihood of inadvertent ignition is reduced.